Method and apparatus for controlling the expansion and retraction of a telescopic cylinder assembly

ABSTRACT

In a double-acting telescopic hydraulic cylinder assembly, a counter-pressure in the discharge chambers is provided, opposing those into which fluid under pressure is supplied. Said counterpressure is obtained by providing discharge valves which are gauged so as to permit discharge of the fluid to be expelled only when a predetermined pressure value of the fluid in the said discharge chambers is attained.

g United States Patent [151 3,691,904

Pesci [451 Sept. 19, 1972 [54] METHOD AND APPARATUS FOR 3,170,377 2/ I965 Herpich et al..; ..9I/I69 CONTROLLING THE EXPANSION AND RETRACTION OF A TELES C on C FOREIGN PATENTS OR APPLICATIONS CYLINDER ASSEMBLY 982,487 1/1951 France ..91/167 [72] Inventor: Arturo Pesci, 37, Via IV Novembre, pi Examiner pau| E. Maslousky n Ferrari, Attorney-Murray Schaffer 22 F1 d: De I7, 19 I 69 57 ABSTRACT Appl' 885680 In a double-acting telescopic hydraulic cylinder assembly, a counter-pressure in the discharge chambers [30] Foreign A li ation Priority Data is provided, opposing those into which fluid under pressure is supplied. Said counter-pressure is obtained Dec. 28, 1968 Italy ..7558 A/68 y providing discharge valves hi are g g so as to permit discharge of the fluid to be expelled only [52] US. Cl. ..91/169, 91/189, 91/447, when a predetermined pressure value of the fluid in 91/454 the said discharge chambers is attained. [51] Int. Cl. ..F0lb 7/00, Fl5b 13/042 [58] Field of Search ..9I/I69, 167, 189, 447, 454

[56] References Cited 6 Claims, 2 Drawing Figures UNITED STATES PATENTS This invention relates to a method and apparatus for controlling the expansion and the retraction of the cylinders of a telescopic cylinder assembly, particularly a double-acting telescopic hydraulic assembly of the type having a plurality of telescoping cylinders and which is particularly adapted for use as a push and pull jack-type attachment for industrial trucks, although many other uses will appear to those skilled in the art.

There are known telescopic hydraulic cylinder assemblies in which the several cylinders-pistons expand or retract in a disorderly or non-sequential manner, due to the presence of passive resistances, such as friction, starting, or inertial forces, and other perturbing forces opposing the active thrusts which, for each pistoncylinder, are determined by the effective working sectional area of the piston and by the value of the pressure acting on said surface, both in the case of the expansion and in'the case of the retraction of the assembly. Thus, it frequently happens that the one cylinder which should expand (or collapse) at first, is actually operated after the expansion (or retraction) of one or more of the other cylinders which themselves should have been operated after the full displacement (in either direction) of the mentioned first cylinder. This disorderly displacement causes serious disturbances in the function of the assembly.

It is therefore a primary object of this invention to provide a method and apparatus for obtaining the orderly or sequential operation, both in expansion and in retraction, of the cylinders of a telescopic pistoncylinder assembly, in such a manner that the said operation takes place exclusively according to an order which is in relation to the working surfaces of the various pistons formed on the movable cylinders, and to the value of the pressure acting on the said working surfaces, irrespectively of any frictional resistances, inertial forces or other perturbing agents.

In accordance with the invention the above object is attained, in a conventional type telescopic cylinder assembly (in which the bases of each cylinder, except the outer one, as well as a central rod are provided with a piston member, thus defining pressure chambers at both opposite sides of each piston member) by providing a suitable counter-pressure in the discharge chambers, i.e., in the chambers opposite to the chambers into which there is supplied the fluid under pressure which effectively promotes the axial shifting of the cylinders. This counter-pressure which counteracts the pressure promoting the shifting, is preferably obtained by providing, on the hydraulic circuit connected to the telescopic assembly, gauged or calibrated discharge valves which will permit the outflow of the liquid expelled by the discharge chambers as a result of the reciprocal sliding of cylinders and pistons only whenever the liquid to be expelled has attained a predetermined pressure value. In order to simplify the description, it will be assumed that, in the case of double-acting telescopic assemblies, the movable members are the cylinders and the discharge valves are two, inasmuch as the positive movement of the cylinders takes place both in the expansion and in the retraction of the assembly.

Other objects and advantages will appear from the following description of an example of the invention, when considered in connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims.

IN THE DRAWINGS FIG. 1 is a diagrammatic view of the apparatus'for obtaining the orderly shifting both in expansion and in retraction of a double-acting hydraulicftelescopic DESCRIPTION OF THE PREFERRED EMBODIMENT The telescopic hydraulic multi-cylinder and piston assembly shown in FIG. 2 of the drawings comprises an outer cylinder 101 closed at its rear end with a bottom plate 201 provided with a base port 301 for attachment of a tubular connection 25, while in proximity of its opposite or front end the outer cylinder 101 is provided with a side port 401 for attachment of another tubular connection 19.

Inside the cylinder 101 a first-stage piston-cylinder unit 3 is slidably mounted. This stage unit 3 comprises a hollow piston rod 103 provided in proximity of its inner end'with an annular piston head 4 slidably mounted with a tight fit in said outer cylinder 101, while the open end of the annular chamber A between said outer cylinder 101 and the hollow piston rod 103 is tightly closed by a sleeve 2. This sleeve, which may be provided with an outer flange for mounting purposes, has a reduced inner end -.section spaced from the wall of cylinder 1 and provided with a plurality or crown of through bores 102 lyin'g substantially in the same crosssectional plane of port 401. Inside of hollow piston rod 103 a co-axial cylinder 203 is inserted with a tight flt at both of its ends, while the intermediate outer surface of said cylinder 203 is spaced from the interior of the hollow piston rod 103 so as to form an annular gap 303, communicating with annular chamber A through a bore 403 formed in correspondence of an annular groove 503 in the outer surface of hollow rod 103, in proximity of the gap end adjacent to said annular piston 4, while the same gap is in communication, at its opposite end, with another chamber A] at the interior of said stage unit 3, by means of bores 603.

Inside of cylinder 203 of the first-stage unit 3, a like second-stage piston-cylinder unit 6 is slidably mounted in like manner, said second stage unit 6 comprising a hollow piston rod, provided with an annular piston 8 and a cylinder co-axially mounted in said piston rod and leaving a gap 106, between its tightly fitting ends.

The rear end of said second stage unit is closed by a base 5 comprising a stepped bottom collar 105 constituting the abutment member for the end of the hollow rod of piston 8, while the opposite end is closed by means of a second sleeve 7 which is formed like the first-named sleeve 2 and has a reduced inner end provided with a crown of through bores 107 opening substantially in front of bores 603 formed in the corresponding end of the first-stage cylinder 203. The hollow piston rod of said second stage unit is also provided with a bore 206 opening in an annular groove in proximity of the piston 8 which forms the movable closure of a second annular cylindrical chamber A1, while the second-stage unit cylinder is provided at its outer end with bores 306 opening in front of a reduced section of a third sleeve 11 forming the closure member of said second-stage un it cylinder. Through the bore of said sleeve 11 the rod of a central piston 12 (which both might be named the third-stage unit) is slidabiy mounted with a tight fit, while the said piston 12 in said last-named cylinder, forms a third annular cylindrical chamber A2. The end of said inner cylinder is closed by a bottom piece 9 formed by an annular step 109 and'a hub provided with an axial bore 209 in line with a like bore 205 of the bottom piece 5 and with the base port 301 of the outer cylinder 101,

Thus, as. said, between the cylinder 101 and the coaxial hollow piston rod 103 a first annular cylindrical chamber A is formed, while between the hollow piston rod of the second stage unit 6 and the inner cylinder 203 of the first-stage unit 3 a second annular cylindrical chamber A1 is formed and a third like chamber A2 is formed in the space enclosed all around the said central piston rod 10, which, as said, together with its piston 12, will be termed the third-stage unit.

The whole apparatus will be now described referring to both FIGS. 1 and 2. The just-described telescopic assembly l is connected through side port 401 by means of conduits 17-48-19 to the outlet of a unidirectional free-inflow valve 13 and to the inlet of a calibrated discharge valve 14, while the base port 301 of the telescopic assembly 1 is connected by means of conduits or pipings 23 2425 to the outlet of a unidirectional inflow valve 15 and to the inlet of a calibrated discharge valve 16.

The outlet of discharge valve 16 is connected through conduit 26 to'the inlet of valve 15. The inlets of the delivery valves 13 and 15 are connected through pressure conduits 20 and 22 to two separate ways of the distributing valve D so that they may be singularly and separately fed with liquid under pressure.

The distributing valve D is fed through the delivery conduit M of a high pressure pump P, connected through a suction conduit E to a tank S for the operating fluid (mineral oil).

The distributing valve D is constructed in such a manner that in its neutral position the valves 13 and 15 are not fed, and therefore the oil under pressure delivered by pump P is discharged through conduit into tank S. Distributing valve D must be moreover constructed in such manner that, whenever it feeds the valve 13 through conduit 20, conduits 26 and 22 of the discharge valve 16 are connected to the discharge duct 30 of the distributing valve itself.

The outlet of valve l4, in a different manner with respect to valve 16, is directly connected to the tank S through conduit 21.

Conduit 25 of the telescopic assembly 1 is ,further connected, through conduits 28 and 29 and a suitable cock R, directly to the tank S.

The gauging or calibration of valve 14 must be calculated and adjusted in such a manner as to determine a counter force or braking force which keeps the whole telescopic assembly in collapsed or retracted position,

whenever to the same assembly thereis appliedan extension force equal to the maximum operational force. The gauging or calibration of valve 16 must be calculated at the pressure value which is capable of maintaining the telescopic assembly in its expanded position whenever to same there is applied a retracting force corresponding to the maximum .retracting force which can be obtained by the whole telescopic unit.

Moreover, valve 14 must be gauged or calibrated at such a pressure value, corresponding to the maximum pressure value to which the annular chambers AA1-A can be subjected, in order to operate also as safety valve.

OPERATION By acting on the distributing valve D (with cock R in closed position) so that same feeds oil under pressure to valve 15, it is obtained in practice'that distributing valve D feeds, liquid under pressure to port 301 of the telescopic assembly 1 which takes up from pump P an increasing pressure, thus fully expanding in the order which provides that the outer stage unit 3 slides out first, followed in succession by the-inner stage units 6 and 10-12. I v 1 During this outward stroke or expansion, the oil in the annular chambers A1 and A2 escapes out of port 401 through discharge valve 14 which has been gauged or calibrated at a pressure value which is by far greater than the maximum pressure value of the oil in the delivery side for the full expansion of the telescopic unit, so that it is possible to effect the recovery of this liquid (which though in minimum quantity, would disperse its potential energy into tank S) by conveying same (through a suitable pressure reducing unit not shown into the delivery conduit M of pump P.

By acting now on the distributing valve D to perform the reverse stroke or retraction of the whole telescopic assembly 1, Le, by feeding oil under pressure to'port 401 of same through valve 13, the said distributing valve D now connects the discharge valve 16 to the tank S through conduits 22 and 30.

In the fully expanded position, the stage unit which is i subjected to the lesser braking force by the action-of the gauged discharge valve 16 is the innermost stage unit 10-12 of the telescopic assembly, followed in succession, by the stage units 7 and 3 from the interior to the exterior. Thus the whole telescopic unit is retracted according to an order which provides first for the inward movement of the innermost stage, and subsequently of the following outer stages.

In the operation of the apparatus, it is particularly convenient to open the cock R which short-circuits the discharge valve 16, whenever the telescopic assembly must be retracted in contrast to the maximum operational force of the whole assembly itself, such as may be lifting (pushing up) of a heavy load in vertical direction.

In fact, by short-circuiting discharge valve 16 due to the opening of cock R, it is obtained that under equal conditions of maximum delivery pressure inside annular space A, A1, A2 through valve13, the telescopic assembly can perform greater action because the counter-pressure caused by discharge valve 16 comes to cease, while also in this case the correct order of retraction of each stage is ensured inasmuch as the resisting force (heavy load) in antagonism to the retraction force of each single cylinder-piston unit takes the place of the braking force created by the gauging or calibration of valve 16.

It is obvious that the same principle of short-circuiting the discharge valve through interception means can be applied also when the telescopic assembly 1 is in the condition to perform an expansion stroke against the action of its maximum operational force.

MODIFICATIONS It is understood that the above description has been made with reference to a preferred embodiment of the apparatus according to the invention with the omission of constructive details regarding the distributing valve D, inasmuch as they-can be easily devised and realized by any person skilled in the art, said distributing valve being for example capable of incorporating the cock R. In this case, when the distributing valve Dv must feed valve 13, same can be constructed so as to feed either valve 13 while the discharge is effected as above mentioned through the discharge valve 16 and conduits 22-30, or in another position to feed the said valve 13 and in the meantime to connect port 301 directly to the discharge circuit of the distributing valve D to tank S.

Also, the delivery valves 13 and 15 and the discharge valves 14 and 16 have been illustrated merely by way of example in order to better point the need of gauging or calibration of the discharge. is therefore evident that any other type of valve which may be different from the needle valve, but which can also be gauged or calibrated in accurate manner, can be used to this purpose.

Further, the discharge and delivery valves may be embodied in a single housing or manifold which is provided with inner ducts taking the places of the outer connecting conduits for the connection of the parts.

It is believed that the invention will have been clearly understood from the foregoing detailed description of my now preferred illustrated embodiment. Changes in the details of construction may be resorted to without departing from the spirit of the invention and it is accordingly my intention that no limitations be implied and that the hereto annexed claims be given the broadest interpretation to which the employed language fairly admits.

1 claim:

, l. Telescoping cylinder apparatus comprising 1. a plurality of spaced hollow cylinders having a base at one end telescopically arranged one inside the other, the bases of each cylinder except the outer one being provided with a piston member so as to define pressure chambers at both opposing sides of each piston member, v

2. means serially interconnecting the pressure chambers on one side of each of said pistons and means serially'connecting the pressure chambers on the other side of said pistons,

3. said assembly having two ports, one for each series of communicating pressure chambers and conduits connected to each of said ports which are adapted to alternately act as delivery conduit of the fluid under pressure or discharge conduit of the expelled fluid;

4. each one of the two conduits being subdivided into two branches, one branch serving as delivery duct for the fluid under pressure, and the other branch serving as discharge duct of the expelled fluid;

5. a unidirectional inflow valve provided in each delivery duct, through which flows the liquid under pressure for the displacement of the pistonscylinders;

6. a calibrated valve provided on each discharge branch duct, each calibrated valve serving as discharge valve for the liquid expelled from the chambers opposite to the. chambers into which there issupplied the liquid underpressure;

7. distributing means for supplying the liquid under pressure to either one of the unidirectional inflow valves and consequently to the relating pressure chambers; and

8. pump means for pumping liquid under pressure to said distributing means.

2. An apparatus according to claim 1 in which the calibrated valve is a discharge valve through which the liquid is expelled during the expansion of the telescopic assembly is calibrated at such a pressure value which would be sufficient to maintain the assembly in its retracted position when to the same there is applied an expansion force equal to the maximum operating force of the assembly, while the discharge valve through which the liquid is expelled during the retraction of the telescopic assembly is calibrated at such a pressure value which would be sufficient to maintain the assembly in its expanded position when to the same is applied a retraction force equal to themaximum operating force of the assembly.

3. An apparatus according to claim 2 including a tank for storage of liquid and in which the discharge valve through which the liquid is expelled during the expansion of the telescopic assembly is directly connected to the tank for the liquid, said discharge valve also operating as safety valve during the retraction movement wheneverthe value of pressurein the related chambers becomes greater than the value of pressure at which the said discharge valve has been calibrated.

4. An apparatus according to claim 3 including means for connecting the discharge valve through which the liquid is expelled to said tank so that during the retraction of the telescopic assembly said valve communicates with said tank, while during the expansion movement said connection is inoperative.

5. An apparatus according to claim 2 including conduit means for connecting the distributing means to the unidirectional inflow valve for the expansion-of the telescopic assembly, said discharge valve being connected to said conduit, whereby said conduit acts during the retraction movement of the assembly, as discharge conduit by connecting the outletof the said discharge valve to the tank through the distributing device.

6. An apparatus according to claim 1 including conduit means interposed between said tank and the discharge of each chamber by which the liquid expelled by the chambers opposing the chambers to which the liquid is supplied under pressure may be selectively discharged into the tank through a conduit which short circuits the discharge valves. 

1. Telescoping cylinder apparatus comprising
 1. a plurality of spaced hollow cylinders having a base at one end telescopically arranged one inside the other, the bases of each cylinder except the outer one being provided with a piston member so as to define pressure chambers at both opposing sides of each piston member,
 2. means serially interconnecting the pressure chambers on one side of each of said pistons and means serially connecting the pressure chambers on the other side of said pistons,
 3. said assembly having two ports, one for each series of communicating pressure chambers and conduits connected to each of said ports which are adapted to alternately act as delivery conduit of the fluid under pressure or discharge conduit of the expelled fluid;
 4. each one of the two conduits being subdivided into two branches, one branch serving as delivery duct for the fluid under pressure, and the other branch serving as discharge duct of the expelled fluid;
 5. a unidirectional inflow valve provided in each delivery duct, through which flows the liquid under pressure for the displacement of the pistons-cylinders;
 6. a calibrated valve provided on each discharge branch duct, each calibrated valve serving as discharge valve for the liquid expelled from the chambers opposite to the chambers into which there is supplied the liquid under pressure;
 7. distributing means for supplying the liquid under pressure to either one of the unidirectional inflow valves and consequently to the relating pressure chambers; and
 8. pump means for pumping liquid under pressure to said distributing means.
 2. means serially interconnecting the pressure chambers on one side of each of said pistons and means serially connecting the pressure chambers on the other side of said pistons,
 2. An apparatus according to claim 1 in which the calibrated valve is a discharge valve through which the liquid is expelled during the expansion of the telescopic assembly is calibrated at such a pressure value which would be sufficient to maintain the assembly in its retracted position when to the same there is applied an expansion force equal to the maximum operating force of the assembly, while the discharge valve through which the liquid is expelled during the retraction of the telescopic assembly is calibrated at such a pressure value which would be sufficient to maintain the assembly in its expanded position when to the same is applied a retraction force equal to the maximum operating force of the assembly.
 3. An apparatus according to claim 2 including a tank for storage of liquid and in which the discharge valve through which the liquid is expelled during the expansion of the telescopic assembly is directly connected to the tank for the liquid, said discharge valve also operating as safety valve during the retraction movement whenever the value of pressure in the related chambers becomes greater than the value of pressure at which the said discharge valve has been calibrated.
 3. said assembly having two ports, one for each series of communicating pressure chambers and conduits connected to each of said ports which are adapted to alternately act as delivery conduit of the fluid under pressure or discharge conduit of the expelled fluid;
 4. each one of the two conduits being subdivided into two branches, one branch serving as delivery duct for the fluid under pressure, and the other branch serving as discharge duct of the expelled fluid;
 4. An apparatus according to claim 3 including means for connecting the discharge valve through which the liquid is expelled to said tank so that during the retraction of the telescopic assembly said valve communicates with said tank, while during the expansion movement said connection is inoperative.
 5. An apparatus according to claim 2 including conduit means for connecting the distributing means to the unidirectional inflow valve for the expansion of the telescopic assembly, said discharge valve being connected to said conduit, whereby said conduit acts during the retraction movement of the assembly, as discharge conduit by connecting the outlet of the said discharge valve to the tank through the distributing device.
 5. a unidirectional inflow valve provided in each delivery duct, through which flows the liquid under pressure for the displacement of the pistons-cylinders;
 6. a calibrated valve provided on each discharge branch duct, each calibrated valve serving as discharge valve for the liquid expelled from the chambers opposite to the chambers into which there is supplied the liquid under pressure;
 6. An apparatus according to claim 1 including conduit means interposed between said tank and the discharge of each chamber by which the liquid expelled by the chambers opposing the chambers to which the liquid is supplied under pressure may be selectively discharged into the tank through a conduit which short-circuits the discharge valves.
 7. distributing means for supplying the liquid under pressure to either one of the unidirectional inflow valves and consequently to the relating pressure chambers; and
 8. pump means for pumping liquid under pressure to said distributing means. 